An oil-in-water emulsion is one in which oil droplets are dispersed in a continuous aqueous phase. A water-in-oil emulsion is one in which water droplets are dispersed in a continuous oil phase. In either case, the emulsion is commonly stabilized with synthetic surfactants. Oil-in-water emulsions are best stabilized with surfactants having hydrophilic lipophilic balance (HLB value) of around 5. Water-in-oil emulsions are suitably stabilized with surfactants having HLB values of around 14.
Characteristics of emulsions vary according to the nature of the surfactant with which they are stabilized. The surfactants may be anionic, cationic or neutral. Normally the type of stabilization of the latex has an influence on the means by which they latex may be destabilized.
Breaking of such emulsions into their component phases, e.g. for separation thereof, is often of industrial importance. For example, industrial effluents often contain waste oils, the permissible levels of discharge of which are low and closely regulated. If, as often happens, the oil residues exist in the effluent as an emulsion in the aqueous phase, then separation and removal of the oil creates difficulties. First, the emulsion must be broken before effecting separation of the oil can be undertaken. Also, in industrial processes such as synthetic rubber manufacture, chemical reactions are conducted in an emulsion. The emulsion must, however, be de-stabilized and broken for efficient recovery of the product. There is therefore an industrial need for simple, rapid and efficient processes for breaking oil-water emulsions.